linux-kernel - Re: RCU init call bootmem allocation after slub us ready.

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Date:	Mon, 6 May 2013 13:13:22 -0700
From:	Yinghai Lu <yinghai@...nel.org>
To:	Paul McKenney <paulmck@...ux.vnet.ibm.com>
Cc:	Ingo Molnar <mingo@...e.hu>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: RCU init call bootmem allocation after slub us ready.

On Mon, May 6, 2013 at 1:06 PM, Paul E. McKenney
<paulmck@...ux.vnet.ibm.com> wrote:
> On Mon, May 06, 2013 at 12:06:11PM -0700, Paul E. McKenney wrote:
>> On Mon, May 06, 2013 at 11:53:56AM -0700, Yinghai Lu wrote:
>> > [    0.000000] SLUB: Genslabs=15, HWalign=64, Order=0-3, MinObjects=0,
>> > CPUs=160, Nodes=8
>> > [    0.000000] Hierarchical RCU implementation.
>> > [    0.000000]  RCU restricting CPUs from NR_CPUS=4096 to nr_cpu_ids=160.
>> > [    0.000000] ------------[ cut here ]------------
>> > [    0.000000] WARNING: at mm/nobootmem.c:234
>> > ___alloc_bootmem_nopanic+0x3a/0x7d()
>> > [    0.000000] Modules linked in:
>> > [    0.000000] CPU: 0 PID: 0 Comm: swapper/0 Not tainted
>> > 3.9.0-yh-10495-gfc7ffbc-dirty #1543
>> > [    0.000000] Hardware name: Oracle Corporation  Sun Fire X4800 M2 /
>> >    , BIOS 15013200    04/19/2012
>> > [    0.000000]  0000000000000009 ffffffff82a01e58 ffffffff8209dc61
>> > ffffffff82a01e98
>> > [    0.000000]  ffffffff8108a9d0 0000000000000000 0000000000000000
>> > 0000000000000200
>> > [    0.000000]  ffffffffffffffff 0000000000000040 0000000000000000
>> > ffffffff82a01ea8
>> > [    0.000000] Call Trace:
>> > [    0.000000]  [<ffffffff8209dc61>] dump_stack+0x19/0x1b
>> > [    0.000000]  [<ffffffff8108a9d0>] warn_slowpath_common+0x70/0xa0
>> > [    0.000000]  [<ffffffff8108aa1a>] warn_slowpath_null+0x1a/0x20
>> > [    0.000000]  [<ffffffff82dd54cd>] ___alloc_bootmem_nopanic+0x3a/0x7d
>> > [    0.000000]  [<ffffffff82dd5695>] __alloc_bootmem+0x12/0x38
>> > [    0.000000]  [<ffffffff82de976a>] alloc_bootmem_cpumask_var+0x1a/0x21
>> > [    0.000000]  [<ffffffff82dce4da>] rcu_init+0x66/0x283
>> > [    0.000000]  [<ffffffff82dd15ed>] ? perf_event_init+0x136/0x15f
>> > [    0.000000]  [<ffffffff82dabf95>] start_kernel+0x24a/0x423
>> > [    0.000000]  [<ffffffff82dababe>] ? repair_env_string+0x5e/0x5e
>> > [    0.000000]  [<ffffffff820936b6>] ? __memblock_reserve+0x81/0x89
>> > [    0.000000]  [<ffffffff82dab5a8>] x86_64_start_reservations+0x2f/0x31
>> > [    0.000000]  [<ffffffff82dab79e>] x86_64_start_kernel+0x1f4/0x1fc
>> > [    0.000000] ---[ end trace 53ae8bb075006d8f ]---
>>
>> Do you have commit fa0f93cd6a (rcu: Don't allocate bootmem from rcu_init())?
>> If not, could you please try applying it?
>
> As Dave Jones pointed out, this one is not yet in mainline.  Here is the
> corresponding patch.

Yes, found that in you reply to Dave Jones.

>
>                                                         Thanx, Paul
>
> ------------------------------------------------------------------------
>
> rcu: Don't allocate bootmem from rcu_init()
>
> When rcu_init() is called we already have slab working, allocating
> bootmem at that point results in warnings and an allocation from
> slab.  This commit therefore changes alloc_bootmem_cpumask_var() to
> alloc_cpumask_var() in rcu_bootup_announce_oddness(), which is called
> from rcu_init().
>
> Signed-off-by: Sasha Levin <sasha.levin@...cle.com>
> Signed-off-by: Paul E. McKenney <paulmck@...ux.vnet.ibm.com>
> Reviewed-by: Josh Triplett <josh@...htriplett.org>
>
> diff --git a/kernel/rcutree_plugin.h b/kernel/rcutree_plugin.h
> index ca6e39c..44b0998 100644
> --- a/kernel/rcutree_plugin.h
> +++ b/kernel/rcutree_plugin.h
> @@ -86,7 +86,7 @@ static void __init rcu_bootup_announce_oddness(void)
>  #ifdef CONFIG_RCU_NOCB_CPU
>  #ifndef CONFIG_RCU_NOCB_CPU_NONE
>         if (!have_rcu_nocb_mask) {
> -               alloc_bootmem_cpumask_var(&rcu_nocb_mask);
> +               alloc_cpumask_var(&rcu_nocb_mask, GFP_KERNEL);

alloc_bootmem will return zeroed buffer.

so need to use zalloc_cpumask_var instead.


>                 have_rcu_nocb_mask = true;
>         }
>  #ifdef CONFIG_RCU_NOCB_CPU_ZERO
>
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